(1) Field of the Invention
The present invention relates to a fuel control system of an internal combustion engine, and more particularly to a fuel control system of an internal combustion engine which can precisely achieve an air-fuel ratio control precision in each of operating ranges of the internal combustion engine, in detail, a demanded air fuel ratio at a time of an engine transition period.
(2) Description of Related Art
As a fuel control apparatus of an internal combustion engine, there is a structure which stores a balanced adhering amount of a fuel film with respect to a cooling water temperature of an internal combustion engine (an engine), determines a base fuel film correction amount with respect to a base fuel, further prepares an air intake valve predictive temperature, determines an engine temperature unbalanced state such as a warming up or the like in the case that a difference exists between the cooling water temperature and the air intake valve predictive temperature, calculates a fuel film correction amount of the temperature unbalanced state in correspondence to the temperature difference, and adds to the base fuel film correction amount so as to correct (for example, patent document 1 (JP-B2-3562026)).
The conventional method mentioned above takes into consideration the temperature transition period of the engine such as the warming up or the like, however, does not take into consideration a macroscopic temperature change in a place to which the fuel film is actually adhered. For example, in the conventional method, there is no difference between a cooling water temperature and an air intake valve predictive temperature after the warming up, and the temperature balanced state is determined. Thereafter, the fuel is only corrected on the basis of the change of the balanced fuel film amount in accordance with the region. In other words, the same amount of correction is always applied in the repeat of the transition under the same condition.
However, the temperature at the position to which the fuel film is adhered is changed before and after the transition, on the basis of a heat quantity of the fuel, a heat transmission from the air intake valve, and a heat quantity absorbed by the intake air amount, the adhesion of the fuel, and an evaporation from the fuel film are differentiated in accordance with the change of the temperature, and the fuel film amount is also changed. In the repeat of the transition under the same condition, in order to achieve the demanded air fuel ratio, it is necessary to carry out the correction in correspondence to the fuel film amount change in accordance with the heat quantity change.